OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is a consequence of lactic acid buildup during anaerobic respiration?

1. Increased energy production

2. Improved muscle efficiency

3. Fatigue

4. Enhanced performance

The correct answer is: Fatigue

During anaerobic respiration, when the oxygen supply is limited, glucose is converted into energy and lactic acid is produced as a byproduct. The accumulation of lactic acid in muscles leads to several physiological changes that can contribute to fatigue. This is because lactic acid lowers the pH in muscle tissues, interfering with muscle contractions and overall muscle function. As the lactic acid builds up, it can cause discomfort and a feeling of heaviness in the muscles, ultimately leading to a decrease in performance. The other options do not accurately reflect the consequences of lactic acid buildup. Increased energy production is not the case since the energy yield from anaerobic respiration is lower compared to aerobic respiration. Improved muscle efficiency and enhanced performance are also not outcomes associated with lactic acid buildup; instead, they are usually impaired by it. Understanding the role of lactic acid in muscle fatigue is important for grasping the effects of different respiration processes during physical activity.